Choosing the Right Engine Oil

Did you know that automotive professionals define the following as severe driving conditions?

• Stop-and-go traffic wherein the engine idles or runs at low speeds for extended periods.
• The car is driven mostly on trips that are usually less than 32 kilometers or 30 minutes.
• The car is operated in an area where the surrounding temperature goes below 0oC or above 32oC.
• The car is operated in a dusty or industrialized area.
• The car is driven consistently at high speed when the surrounding temperature is over 32oC.
• The car is used to tow a trailer.

Right off, one would realize immediately that everyday driving around Metro Manila - or most other places in the Philippines, for that matter - means operating a vehicle under severe driving conditions. Which makes the case for choosing the right oil a strong and important consideration for all vehicle owners in the Philippines.

So, how do you choose the right oil for your car's engine?
There are three factors to consider:

1. the company that refined the oil;
2. the engine oil service classification; and
3. the engine oil viscosity rating.

The first factor concerns the engine oil's quality. Go for an engine oil with a well-known name brand or is a product of an established and recognized oil company. This way, you can be fairly sure that the oil is of high quality and contains the necessary additives to perform the many essential functions of an engine oil.

Next, choose an engine oil that has a service classification appropriate for your vehicle engine. In the early 1970s, the American Petroleum Institute (API), the American Society for Testing and Materials (ASTM), and the Society of Automotive Engineers (SAE) established an engine oil service classification system that is now accepted as a universal standard. (Hence the "API" and "SAE" acronyms printed on oil cans.)

Under this letter-grading system, oils classified as applicable for gasoline engines are designated "S," which stands for spark-ignition, and oils classified as applicable for diesel engines are designated "C," for compression-ignition. While many oils in the market today are rated "S" and "C" -- meaning they are applicable for both gas and diesel engines, "S" or "C" oils are generally classified further according to their engine protection capability and the level of work the particular engine will be subjected to. This added classification is also a letter index written next to the engine oil's S or C designation. For instance, an engine oil labeled "API SA" is applicable for gasoline engines, has no special engine protection capabilities and is only suitable for gas engines operating under mild conditions. Engine oils with a higher-letter index after their "S" or "C" classification are better than those with a lower-letter index. Choose them, or the type recommended by your car manufacturer - see your Owner's Manual.

The third factor to consider refers to the engine oil viscosity. Viscosity describes how the engine oil flows at a given temperature. An engine oil of low viscosity, sometimes referred to as a "light oil," flows more easily than an oil of high viscosity, sometimes referred as "heavy oil." As a fluid, oil's viscosity changes with temperature. When it is hot, the oil thins and flows easily; when it's cold, the oil thickens, it becomes more viscous. The engine oil you select for your car engine should then be compatible with the ambient temperature in the area where you drive to ensure that the oil will not thin out and flow too rapidly in hot weather, or thicken and flow sluggishly in cold weather. In either case, engine parts will be deprived of adequate lubrication.

An engine oil's viscosity rating indicates the ambient temperature range within which it has been rated for use. The viscosity rating of an engine oil is prominently printed on the can along with its service classification. This numeric index is preceded usually by "SAE", the acronym of the American group (mentioned earlier) that assigns numbers to oils of different viscosities. Under the viscosity grading system devised by the SAE, likewise acknowledged as a universal standard, the lower the viscosity of an engine oil -- the thinner the oil, the lower the number assigned to it. An engine oil rated SAE 10, for example, is recommended for coId weather operation since it has low viscosity and flows more easily even when the ambient temperature is cold. On the other hand, an engine oil rated SAE 30 is recommended for warm weather operation because it has high viscosity - it is thicker -- and thus will not thin out too much and flow too easily even at high temperatures. (Apart from viscosity though, SAE numbers do not specify any quality of an engine oil.)

SAE 10 or SAE 30 engine oil is an example of a single-viscosity or single weight oil that is restricted for use in a limited temperature range. In contrast, multi-viscosity/multi-weight, or multi-grade oils (as they are called now) are suitable for a much wider temperature range. Because of the viscosity-improver additive mixed into them, which minimize the change in their viscosity, multi-grade oils have the viscosity of an SAE 10 oil when cold, and the viscosity of an SAE 30 oil when hot. A typical multi-viscosity oil is stamped SAE 10W-30 (meaning it can be used in areas where the ambient temperature ranges from -18oC to above 38oC) or SAE 20W-50 (meaning it can be used in areas where the ambient temperature ranges from -12oC to over 38oC; the "W" stands for winter.) Go for multi-grade oils with an SAE grade of 10W-30 or higher.

Aside from the alpha-numeric code printed on the can, some engine oils are labeled "Energy Conserving." These are lower viscosity oil blends which reduce internal engine friction, thereby improving performance and reducing fuel consumption. There are two categories of Energy Conserving (EC) engine oils: EC I and EC II. EC II-labeled engine oils provide better fuel-economy improvement than EC I oils. (Before using Energy Conserving oil, check your Owner's Manual if the manufacturer approves its use in your car's engine.)

While most engine oils are refined from crude oil, some are artificially made by chemical processes and do not necessarily come from petroleum. These are called synthetic oils. Termed synthetic because they are not obtained directly from petroleum (a natural product), synthetic oils flow more easily than many natural oils especially at extremely low temperatures. At the same time, synthetic oils tolerate heat better while producing less sludge and carbon deposits. This is one reason why synthetic oils are much more expensive than natural ones. (Caution: synthetic oils tend to flow so easily that a minor oil leak in your engine can become a major hemorrhage. So make sure your car's engine doesn't leak at all if you choose synthetic oil for your car.)

High price aside, synthetic oils are classified and rated just like other petroleum-based engine oils. Are synthetic oils better? No doubt yes. The question is, can you afford it? Whether you choose synthetic oil or natural, don't forget to follow the oil change interval recommended by your car's manufacturer.